FIG. 1 illustrates a Relay Node (RN) 120 and User Equipments (UEs) 141 and 142 within the coverage of a single evolved Node B (eNB or eNodeB) 110 in a wireless communication system. The RN 120 may forward data received from the eNodeB 110 to the UE 142 within the area of the RN 120, and forward data received from the UE 142 within the area of the RN 120 to the eNodeB 110. Further, the RN 120 may support extension of a high-rate area, an increase in communication quality at a cell edge, and providing of communication to an area outside the coverage of the eNodeB 110. In FIG. 1, there are a UE that receives a service directly from an eNodeB (hereinafter, referred to as a macro-UE or M-UE), such as the UE 141, and a UE that receives a service through the RN 120 (hereinafter, referred to as a Relay-UE or R-UE), such as the UE 142.
A radio link between the eNodeB 110 and the RN 120 is defined as a backhaul link. A link directed from the eNodeB 110 to the RN 120 is called a backhaul downlink, and a link directed from the RN 120 to the eNodeB 110 is called a backhaul uplink. Meanwhile, a radio link between the RN 120 and the UE 142 is defined as an access link. A link directed from the RN 120 to the UE 142 is called an access downlink, and a link directed from the UE 142 to the RN 120 is called an access uplink.
If the RN 120 autonomously controls a cell, the UE 142 may perceive the RN 120 as a general eNodeB. On the other hand, if another UE functions as the RN 120 (this RN is referred to as a UE-relay), the UE 142 may not recognize the existence of the RN 120.